NEAR-SURFACE PERMAFROST GROUND ICE CHARACTERISTICS AND ECOLOGICAL AND PHYSICAL DRIVERS OF TRANSIENT LAYER ICE CONTENT IN DISCONTINUOUS PERMAFROST

• Main Author: Paul, Jason
• Format: Text
• Language: English
• Published: Scholars Commons @ Laurier 2018
• Subjects: Great Slave Lowland; boreal; Picea mariana; Picea glauca; Betula papyrifera; frost susceptible sediments; Integrative Biology; Other Earth Sciences; Terrestrial and Aquatic Ecology; North Slave Region; Yellowknife; Active layer thickness; Ice; permafrost
• Online Access: https://scholars.wlu.ca/etd/2097; https://scholars.wlu.ca/context/etd/article/3215/viewcontent/Jason_Paul___MSc_Thesis___Final.pdf

Accelerated climate warming in northern regions is causing permafrost degradation, leading to the reduction of the areal extent of permafrost. Permafrost is the foundation for many northern ecosystems and communities, so its thaw can have important ecological and societal consequences. Thaw of ice-rich permafrost can cause subsidence of the ground surface proportional to excess ice content. Terrain settlement can cause ponding or damage to infrastructure. Following a surface disturbance that removes much of the vegetation cover, a shift in the ground thermal regime can cause an increase in active layer thickness and rapid thaw of the top portion of permafrost. This upper layer of permafrost is known as the transient layer because it thaws and re-aggrades on multi-decadal to centennial timescales in association with ecosystem disturbance or climate change. Understanding the processes that lead to ice-enrichment of the transient layer can help us better predict ice-rich areas, and identify ecosystems that are at risk of state changes resulting from permafrost thaw. This research examined the variation of ground ice content of near-surface permafrost, and the factors that influence it in well-drained forests of the discontinuous permafrost zone. The specific objectives of this thesis was to 1) characterize near-surface ground ice content and examine relations between ground-ice, forest type, soil conditions, and permafrost history, and 2) quantify the role of forest characteristics and soil properties as drivers of transient layer ice content, and determine if active layer or ice content are related to ground vegetation communities in this landscape type. Data collection to support these research objectives involved collection of 567 permafrost core samples and completion of soil and vegetation surveys from 10 black spruce and 10 white spruce/birch forests on mineral soils in the North Slave region near Yellowknife, NWT during the summers of 2014 and 2015. In Chapter 2 I found evidence of a permafrost transient ...